This invention relates to the field of heavy duty laundry detergents in liquid form. More specifically it relates to a laundry detergent in the form of a stable, built opaque, viscous liquid in emulsion form, containing suspended solids.
Laundry products in liquid form have been known for some time, but they have never enjoyed the same degree of popularity and commercial success as laundry products in granular form.
One category of liquid laundry products is the optically clear, single phase liquid. Included in this category, for purposes of this disclosure, are compositions all of whose major constituents are present in completely dissolved form but which contain minor amounts, usually below 1%, of suspended material which visually opacifies the product, such as carboxymethyl cellulose or a polymeric emulsion. Such a composition will be referred to hereinafter as a predominantly single phase composition.
One kind of predominantly single phase composition that has been sold for many years consists principally of surfactant, phosphate builder, hydrotrope and water. Typically the surfactant is anionic, the phosphate is tetrapotassium pyrophosphate, and the hydrotrope is potassium toluene sulfonate. Pyrophosphate has been generally preferred to triphosphate as builder because when dissolved in water it exhibits greater chemical stability toward reversion, i.e. toward breakdown to orthophosphate, especially when stored at temperatures above the ambient. To obtain compatibility and mutual solubility between the surfactant and builder a hydrotrope is required which is expensive and yet does not contribute toward the end use of the product, i.e. toward detergency, stain removal sudsing or the like. Even so, expensive potassium builders rather than sodium builders are required to obtain the requisite mutual solubility.
A second kind of predominantly single phase liquid composition has appeared on the commercial scene more recently. Typically it contains a mixture of nonionic and anionic surfactants, the latter being present as the triethanolamine salts, and substantial amounts of free triethanolamine. Such a formula suffers from a lack of builder in the usual sense, i.e. it contains no builders that complex or precipitate Ca.sup.+.sup.+ and Mg.sup.+.sup.+ hardness, either inorganic builders such as a complex phosphate (e.g. triphosphate) or organic builders such as an aminopolycarboxylate (e.g. nitrilotriacetic acid). In addition, relatively large amounts of expensive triethanolamine is required, both in the form of the free base and as the neutralizing cation for the anionic surfactant acid.
A second category of liquid laundry products in the prior art is mull. This consists primarily of colloidal particles of builder suspended in a nonaqueous liquid vehicle. Typically the builder is sodium triphosphate and the vehicle is nonionic surfactant or a mixture of a nonionic surfactant plus a glycol. A detergent mull requires specialized and expensive methods of preparation, and it requires expensive nonaqueous liquid as the vehicle, rather than water. Also, upon contact with small proportions of water during storage or in use, a detergent mull tends strongly to form large crystals and/or gel structures which neither dispense well from the container nor dispense well in the laundering bath. For these reasons the mull has not enjoyed commercial success.
A third category of liquid laundry products, to which this invention belongs, is the emulsion. Detergent emulsions are typically aqueous and contain an isotropic phase (lye or nigre) and an anisotropic phase (neat or middle). Either phase may be continuous. There may be suspended within the emulsion, normally in the continuous phase, finely divided solid particulate material which may be an electrolyte of relatively low solubility such as a phosphate builder, or may be an inert, insoluble material.
To have practical utility, a detergent product in emulsion form must remain physically stable for considerable periods of time, e.e. the phases must not grossly separate to a large degree under normal conditions of storage. Some emulsion compositions require, to achieve satisfactory physical stability, addition of a stabilizing agent such as a resin polymer which is otherwise not useful in the composition. Other emulsion compositions are self-stabilizing: [the prior art has referred to them as autostabilized]; they need only to be properly formulated and processed and do not require the addition of a separate stabilizing agent. Emulsions of both kinds, i.e. those with and those without separate stabilizing agents, typically must be formulated within narrow ranges of composition: changing in a modest way the type surfactant or the builder, or using appreciably more or less of either, ordinarily is enough to cause instability.
The liquid laundry product of the present invention is in the form of an emulsion containing suspended, finely divided solid particles, and will sometimes be referred to hereinafter as an emulsion/suspension. This product form does not require a hydrotrope or a non-aqueous vehicle or solvent, either of which contributes heavily to cost without contributing to effectiveness in the washing process. It uses common raw materials which are widely available at relatively low cost, and it uses them without special purification. Its stabilizing agent is alkali metal sulfate, which in the form of sodium sulfate is already present in the least expensive form of the surfactant raw materials. It permits adjustment of amounts and ratios of the key ingredients over relatively broad ranges so that a formulator can adjust the composition to suit the technical and commercial requirements of himself and his customers. It is stable, both physically and chemically, during substantial periods of time under a wide variety of storage conditions commercially encountered.
All of the above are objects of the present invention which are achieved in the manner disclosed hereinbelow.
Prior Art PA0 a. surfactant in an amount from about 7% to about 25% by weight of the composition, said surfactant consisting of: PA0 b. inorganic phosphate builder in an amount from about 6% to about 25% by weight of the composition, said builder being selected from the group consisting of sodium orthophosphate, sodium pyrophosphate, and sodium tripolyphosphate; PA0 c. alkali metal sulfate in an amount from about 3% to about 20% by weight of the composition as stabilizing electrolyte; and PA0 d. water in an amount from about 40% to about 75% of the composition.
Among the numerous disclosures of single phase, optically clear, liquid laundry compositions the following may be mentioned as representative: U.S. Pat. No. 2,859,182 issued on Nov. 4, 1958 to Carroll; U.S. Pat. No. 2,878,186 issued on Mar. 10, 1959 to Krumrei; and U.S. Pat. No. 3,101,324 issued on Aug. 20, 1963 to Wixon.
U.S. Pat. No. 3,231,504 issued on Jan. 25, 1966 to Marion et al discloses alkyl ether sulfate/alkyl benzene sulfonate mixtures in a predominantly single phase built detergent liquid solubilized with hydrotrope. U.S. Pat. No. 3,574,125 issued on Apr. 6, 1971 to von Paassen discloses alkyl ether sulfate as the sole surfactant in an unbuilt detergent liquid containing a plasticizer such as dibutyl phthalate as well as a conventional hydrotrope.
Typical references relating to liquid laundry compositions the principal components of which form a single phase, optically clear liquid but which have minor amounts of finely divided solid or liquid material suspended therein, are U.S. Pat. No. 2,994,665 issued on Aug. 1, 1961 to Reich et al and U.S. Pat. No. 3,393,154 issued on July 16, 1968 to Treitler. Treitler suggests using neutral salts, e.g. sodium sulfate, in light duty liquids which do not contain alkaline builders such as phosphates.
Unbuilt single phase, optically clear liquid laundry compositions are disclosed in U.S. Pat. No. 3,869,399 issued to Collins on Mar. 4, 1975. Other references to similar compositions are U.S. Pat. No. 3,528,925 issued to Chapuis on Sept. 15, 1970; British Pat. No. 986,049 issued to Imperial Chemical Industries on Mar. 17, 1965; and U.S. Pat. No. 2,875,153 issued to Dalton on Feb. 24, 1959.
Liquid laundry compositions in mull form are disclosed in U.S. Pat. No. 2,864,770 issued to McCune et al on Dec. 16, 1958 and U.S. Pat. No. 3,169,930 issued to Gedge on Feb. 16, 1965.
Representative disclosures of liquid laundry products in emulsion/suspension form are U.S. Pat. No. 2,920,045 issued to Hearn et al on Jan. 5, 1960; U.S. Pat. No. 3,039,971 issued to Cohen on June 19, 1962; U.S. Pat. No. 3,328,309 issued to Grifo et al on June 27, 1967; U.S. Pat. No. 3,346,503 issued to Huggins on Oct. 10, 1967; U.S. Pat. No. 3,351,557 issued to Almstead et al on Nov. 7, 1967; U.S. Pat. No. 3,509,059 issued to Renold on Apr. 28, 1970; U.S. Pat. No. 3,574,122 issued to Payne et al on Apr. 6, 1971; U.S. Pat. No. 3,629,125 issued to Payne et al on Dec. 21, 1971; and Canadian Pat. No. 917,031 issued to Monroe et al on Dec. 19, 1972.
U.S. Pat. No. 3,501,409 issued on Mar. 17, 1970 to Matson et al discloses the use of low molecular weight alkyl ether sulfates as hydrotropes for increasing the solubility of alkyl benzene sulfonate in light- or heavy-duty liquid detergent compositions. The latter were formulated with a potassium polyphosphate as builder. Sodium sulfate was said to enhance detergency but was not an essential component.
U.S. Pat. No. 3,235,505 issued on Feb. 15, 1966 to Tuvell discloses a heavy duty detergent product in which alkyl ether sulfate may be the surfactant, which product is stabilized in emulsion/suspension form by a particular polymeric substance.
Disclosures of detergent liquid emulsion/suspension products in the form of abrasive cleaners are U.S. Pat. No. 3,210,285 issued to Gangwich on Oct. 5, 1965 and U.S. Pat. No. 3,813,349 issued to Wolfson on May 28, 1974. Gangwich used NaCl at levels of 0.25 to 2.5% to stabilize the composition against physical and chemical deterioration upon aging, and found similar though less effective benefits from other salts including Na.sub.2 SO.sub.4.
A liquid laundry emulsion known to have been sold commercially has the approximate composition 14.4% branched chain alkyl benzene sulfonate; 1.8% coconut monoethanol amide; 18.5% sodium triphosphate; 1.6% silicate solids having a weight ratio of SiO.sub.2 to Na.sub.2 O of 2.0:1; 1% sodium sulfate; 0.2% phosphate ester stabilizing agent; minor amounts of carboxymethyl cellulose, optical brightener, formaldehyde and perfume; and the balance water. Low salt ABS paste as described hereinafter was required in this emulsion/suspension to achieve satisfactory physical stability, even though a phosphate ester stabilizing agent was incorporated.